1. Field of the Invention
The present invention relates to a furnace, in particular an electric furnace, for treating liquid metal.
It is in particular applicable to electric arc furnaces employed in the steel industry for producing steels.
2. Discussion of the Background
A furnace is known in the art which comprises a vessel closed by a floating roof.
The floating roof may be raised and displaced for charging the furnace with in particular steel scrap. When the charging has finished, the cover is put back in position on the top of the vessel.
During furnace operation, problems with the seal between the vessel and the floating roof arise.
It is known to ensure the seal between the vessel and the floating roof by means of a joint of sand disposed on the edge portion of the opening of the vessel. Now, owing to the fact that the surface of the sand retains its initial shape when the floating roof is displaced, the joint loses its sealing properties when the roof is again placed on the surface of the sand which no longer closely adapts itself to the shape of the peripheral contour of the roof.
There has therefore been proposed a sealing device between the vessel and the floating roof which comprises a flexible refractory material disposed on the edge portion of the opening of the vessel. This flexible refractory material resumes its initial shape when the roof is raised. Such a sealing device is disclosed in the document FR-A-2 665 756.
In this sealing device, the edge portions of the junction between the floating roof and the vessel are defined by substantially planar and horizontal surfaces. Now, the contact between one planar surface and another planar surface adversely affects the quality of the seal. Further, in the course of the charging of the vessel, steel scrap is deposited on the planar edge portion of the opening of the vessel and this has a harmful effect on the sealing of the furnace when the roof is placed back on the vessel.